This research synthesis analyzes a selection of classroom-based empirical studies on language teacher agency within ESL/EFL/bilingual contexts. Comprehensive analyses of the selected research center on several respects: theoretical frameworks, contexts, methodologies, major findings, methodological and ethical issues as well as implications. In doing this, this paper aims to present ESL/EFL/bilingual teachers' roles as legitimate and agentive actors in their contexts of work, to offer pedagogical implications for teachers and teacher educators, to better inform researchers of current literature and future research directions, and to support possible collaborations among different educational stakeholders.